Step 1) Copy your CAESAR file and delete everything but the vessel. Run the input checker, and it'll tell you how much your caesar model of your vessel weighs and its center of gravity.

Step 2) Find actual weight of vessel and actual center of gravity of vessel.

Step 3) Calculate the difference in weight, and locate the point in CAESAR where applying this mass will result in the CAESAR reported mass and COG match actual mass and COG. You can do so using either a force or a downward-oriented rigid element with mass.

Note 1: If you end up with false reports of overstress in the vessel, then you may distribute the mass.

Note 2: This recommendation is for static analysis only. Additional caution may be warranted on dynamic analysis.